buccal cavity

It is by no means certain that horses connect pressure in the mouth with the rider.  They have not evolved to expect that another animal can apply pressure to the inside of the buccal cavity via a piece of metal.  This cognitive aspect may account for the apparent tolerance (or habituation) horses show when allowing heavy handed riders to mount them time after time.  It is therefore unnecessary and inappropriate to complicate a rider’s interventions by giving them anthropomorphic labels, such as ‘asking’ (e.g asking the horse to lower its head), ‘encouraging’ (e.g. using the inside leg to encourage forward movement) and 'supporting’ (e.g. applying the outside rein to support the impulsion).  It may be the intention to use words that are common in everyday usage and convey an attitude of cooperation rather than supremacy, but the abiding problem with the use of an anthropomorphic framework to explain rider-horse interactions is that it can disguise and justify abuse of horses that offer undesirable responses, even though these may have been accidentally induced/trained by humans.  So, most horses benefit when science provides mechanistic explanations of equitation, even though some horse people argue that this is undermining the bond they share with their horses (McGreevy, 2007).
—  Paul McGreevy & Andrew Mclean ~ Equitation Science